Sample Input for FROZSL: NaCl

The following is sample input for NaCl. We calculate the frequency of the transverse optical (TO) phonon mode at k=0. This is at the gamma point in the first Brillouin zone. In the input below, we indicate the gamma point with GM. Click on the start button below. This produces the output of frozsl_init, giving the frozen phonons that need to be calculated. From the output, we find that there is only one irrep involved: GM4-. There are two symmetry vectors, but since one combination is the acoustic mode at zero frequency, we find that we only need to calculate the energy of one frozen phonon.

In equilibrium, the atomic positions are at

 position of each atom (dimensionless)
    0.000000000000000   0.000000000000000   0.000000000000000
    0.500000000000000   0.000000000000000   0.000000000000000
 position of each atom (cartesian)
    0.000000000000000   0.000000000000000   0.000000000000000
    5.300000000000000   0.000000000000000   0.000000000000000
 Wyckoff positions
   Na  a  z =  0.00000  
   Cl  a  z =  0.50000

We have three choices above for expressing the atomic positions. The third choice gives the Wyckoff position in the isotropy subgroup 107 C4v-9 determined by the distortion produced by the frozen phonon. In the frozen phonon, the atomic positions are at

 atomic positions (dimensionless)
    0.018867924528302   0.000000000000000   0.000000000000000
    0.487763791681082   0.000000000000000   0.000000000000000
 atomic positions (cartesian)
    0.200000000000000   0.000000000000000   0.000000000000000
    5.170296191819464   0.000000000000000   0.000000000000000
 atomic positions (Wyckoff parameters in subgroup)
    0.00000   0.00000   0.07915
    0.00000   0.00000   0.44867

The energy of the frozen phonon is the difference in energy of these two structures. Using a first-principles energy calculation, we find the energy of this frozen phonon to be 0.83 millihartrees. This value has been entered into the energy input field below. Select "output from frozsl" below, and then click on the start button. Now we see the frequencies of the modes: the acoustic mode at zero frequency and the optical mode at 170/cm.